Depending on whether we’re using version Hyperscale (HS1.5) or Hyperscale X (HSX), there are slight differences in how they operate.

In Hyperscale 1.5, it utilizes a Gluster file system that keeps track of all the parts within a disk that have failed. Only when the disk is replaced does it rebuild these parts on the new disk using available parts from other drives (using erasure coding).

In Hyperscale X, the process is slightly different. As soon as the system detects a failure, a Storage Pool Migration occurs immediately (regardless of whether the disk is replaced or not). This process rebuilds the parts that were on the failed disk and places them in alternate locations within the cluster to maintain resiliency. When the disk is replaced, a rebalance process starts to fill up the newly replaced disk

HI Emils

Thank you for the response. I have two questions from above: 

1. the rebuilt data has been kept on the same logical volume from which the disk failed?
2. What is the rebalance process?how exactly it works?
3. Will i be able to perform backup during this process?

1. The rebuilt data is recalculated (Erasure Coding). Recommend reading how erasure code works.
2. Rebalance occurs hourly on the cluster and checks on disk utilization and will try to rebalance based on disk usage.
3. Backups will not be affected during this process.
   1. Review HSX resiliency for more details.